


Undertow

by corbaccio



Category: Shingeki no Kyojin | Attack on Titan
Genre: Alternate Universe - Canon Divergence, Double Penetration, Multi, Plot What Plot/Porn Without Plot, Threesome - M/M/M
Language: English
Status: Completed
Published: 2015-12-12
Updated: 2015-12-12
Packaged: 2018-05-06 09:36:56
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,849
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5411894
Author URL: https://archiveofourown.org/users/corbaccio/pseuds/corbaccio
Summary: <blockquote class="userstuff">
              <p>They've been building up to this for weeks, but now that he’s watching Reiner take himself in hand and Bertholdt’s weight is dipping the mattress, everything seems infinitely more real.</p>
            </blockquote>





	Undertow

**Author's Note:**

> it's been 84 years... well, nearly two. i wrote this originally for a kink meme fill, and i did publish it here before deleting it out of shame. now i no longer have the capacity to feel shame. please enjoy! and, er, suspend your disbelief a little.

They've been building up to this for weeks, but now that he’s watching Reiner take himself in hand and Bertholdt’s weight is dipping the mattress, everything seems infinitely more real. The bed's no more than a cot, really—small for two people, never mind three—so Reiner’s pressed up against the headboard, Armin sat on his lap in such a way that they're face to face. He’s trying to ignore that Reiner's cock looks bigger than he remembers, that Bertholdt is generously sized as well, but the more he thinks about it the more his stomach twists. It’s getting harder to parse the fear from the arousal.   
  
Reiner must sense his nerves, because he brings a hand up to rub the space between his shoulder blades. It’s soothing, familiar, and Armin feels himself relax into the touch.  
  
“You sure you’re okay with this?” says Reiner. He ducks his head to catch Armin’s eye, the little pinch between his brows betraying his concern. Armin leans their foreheads together, the affection easy, unconscious, and Reiner’s expression softens.  
  
“Yes, I’m sure,” he says, because he wants this. He’s been wanting this so much it’s almost a physical ache—something like hunger, Armin thinks, an incessant tugging  _need_. He turns to take in Bertholdt, too, and smiles what he hopes is a reassuring smile. “You don’t have to keep asking. I trust you.”  
  
Bertholdt swallows hard, throat bobbing. “Make sure to say something if it hurts too much, okay?” he says. He looks a little wired, a little nervous, a stark contrast to Reiner's surety.   
  
Armin nods, and he’s about to reply when Reiner’s hand slides to the small of his back, urging him close. He strokes small circles into the base of Armin's spine before dropping lower. His fingers graze against him, pausing a moment before pressing inside, easy, two digits at once.  
  
“You prepared yourself?” Reiner says. There’s something about his tone of voice—it’s not amusement, but rather closer to admiration or pride. Armin’s stomach flips a little.  
  
“I thought it’d be,” he struggles for a moment, blood rushing to his face, “uh, easier, you know. All things considered.”  
  
He hears Bertholdt give a pleasing little sigh, knows from experience that he must be touching himself. Reiner must notice, too, because his gaze flicks past Armin’s face over to him. He grins again, says, “Good idea,” low and dark at Armin’s ear, and, well. Armin is nothing if not one for good ideas. Reiner nudges at his side as he goes on, “Could you turn around?”  
  
The fingers pull out of him and Armin obeys, wriggling off Reiner’s lap to turn his back to him. His erection slides at Armin’s tailbone, wet with precum and oil, the heat of it sending a shiver of anticipation along his spine. Reiner moves into a kneel behind him, one hand at the crease of Armin's thigh, the other guiding his cock into place. Reiner’s slide into him is smooth, all one easy motion as he pulls Armin up against his hips, like he knows the form of his body perfectly. Reiner gives a long, shaky exhale.   
  
“You're doing great,” Reiner murmurs, in that almost fatherly way of his, “really great.”  
  
Armin feels Bertholdt watching him, watching Reiner. There’s a strange sort of tenderness to his gaze, and for whatever reason, it makes Armin's face burn even warmer. Of all times to be embarrassed, he thinks ruefully. But then Bertholdt is edging close, close enough that Armin can feel the heat radiating off him like a wave, and all thought is forgotten. He can’t stop the frantic gasp as two slick fingers circle where Reiner is sheathed within him. Armin swears he can see Bertholdt's pulse flutter as he stares at where they’re joined, before he works his two fingers in alongside. They’re pressed so close, so tight, that Armin can feel Reiner’s erection throb at the added stimulus of his touch, the muscles of his abdomen tensing where they’re flush against Armin’s back. God, they’re both so  _warm_ , thrumming with this peculiar heat that makes his head spin.  
  
Bertholdt’s fingers crook inside him just so, glancing his prostate, and Armin has to bite back the urge to shout. Bertholdt’s voice is quiet and hoarse when he speaks: “Is this... alright?”   
  
“Is it?” Reiner echoes, leaning over Armin's shoulder to study his face. He draws a rough thumb along his cheek, swiping away a bead of sweat there; it’s anchoring, somehow, enough that Armin can find his words again.  
  
“Yes,” he says, taking care to meet Bertholdt’s stare. “Keep going.”  
  
Bertholdt nods, diverting his hand long enough to slide down the sensitive skin of his perineum, gentle, more a reassurance than a tease, but then it’s back to where it was. This time, with an added third finger. Even with the oil, the stretch is painful. They’ve gone this far before, but now it’s leading up to this— _end point_ —and that thought alone has Armin’s insides twisting again. It feels good, though, between the both of them. Like something he could give in to, get lost in. It makes Armin feel small, but not in a bad way. There’s trust in this: that Reiner and Bertholdt recognise his strength, know that he can handle this, the both of them at once. There’s power in that trust.  
  
Bertholdt is tall enough to bend over his shoulder, and the sudden press of hot, damp skin flush against Armin’s front makes him groan, especially when Bertholdt’s erection glides against his own. Reiner rises to meet him in a kiss—deep, intense. Watching them this close, Armin feels a little dizzy. But then it’s over, and Reiner is lifting Armin with impossible ease, moving to give Bertholdt better access. It’s like electricity has been run through all three of them when Bertholdt lines himself up. His cock is slick, hot as a brand at the base of Reiner’s shaft as he nudges forward.  
  
_Fuck_ , Armin tries to say, but his breath escapes him in this awful strangled rush, and he can’t get any sound out, can’t think beyond the slow torturous stretch of Reiner and Bertholdt both. His hips jerk, one hand thrown back to curl into Reiner’s hair, the other scoring marks into the muscle of Bertholdt’s shoulder.  
  
Reiner pants a curse into his ear. “Stop, Bertl, stop,” he says, breathless, like it takes all the willpower in the world. “Armin, d’you want to...?”  
  
“Wait,” is all he can manage at first, because they’ve stopped and he can think again, can breathe. But no, he doesn’t  _want_  to stop, and the sharp impossible edge of the stretch has faded a little. Not by much, but enough. “Just... just give me a minute, please.”  
  
He can feel the line of Bertholdt’s jaw, sweat-slick, tentative, at the junction of his shoulder. It’s a question, Armin knows—has come to know, and after a long moment he nods.  
  
They take it slower, this time. Armin can’t tell whether that’s better or worse. Reiner’s hands are sure and firm between his thighs, spreading him further as Bertholdt moves in minute increments. He has the kind of self-control that’s at once blessed and frustrating. When Armin moans, a raw, open sound, Reiner pulls at his chin to draw him into a kiss, giving Armin’s bottom lip a gentle tug before taking his tongue into his mouth. Armin knows it’s a distraction, but he needs one, needs Reiner, and he lets the kiss leave him boneless. It’s almost bearable, like this. With Reiner’s hot, calloused hand moving to cup his erection against his stomach, the other rubbing soothing shapes into his side as Bertholdt shifts inside him, against him.  
  
Reiner breaks the kiss to gasp. “Oh fuck, Bertholdt, I can  _feel_  you,” he says, and Armin wonders how he can still form full sentences.  
  
Finally—and the relief is almost enough to make Armin cry—Bertholdt is buried inside him. Armin huffs and tries to rock a little higher on his knees, but  _god_ , all he can feel is how tight Reiner’s curled around his back, how deep Bertholdt is inside him, how wide he’s been split open. It’s all magnified with his eyes shut: the two of them moving in tandem, sliding against each other, the constant push at his prostate, his erection trapped against Bertholdt's stomach. The pressure is abrupt and overwhelming, fullness sweeping through him like a current. Reiner noses at his temple as he chokes for air.  
  
“It’s okay, you’re okay,” he says, gentle, almost reverent, “you’re doing so good for us, Armin.”  
  
Armin feels his voice more than hears it, the rumble of Reiner’s chest, the way his mouth moves against the shell of his ear. He’s too warm, too full. Armin takes one, two, three deep breaths, the air blissfully cool. One of Bertholdt’s hands is moving down his front, palm pressed flat to his belly; it dips just low enough for his knuckles to graze the head of Armin’s cock and he jolts without meaning to. Armin must clench tight around the both of them, because he recognises Reiner’s moan, Bertholdt’s watery exhale.  
  
“D-do you want me to—” Bertholdt stutters, face hot where it’s pressed against the slope of Armin’s brow bone. He doesn’t go on, but it’s obvious what he’s asking when long fingers wrap around Armin’s erection. He fits easily into Bertholdt’s hand, the round of his palm rough at the base of Armin’s cock. The burn of the stretch is enough to keep him from coming just yet, but he nods wildly.  
  
“God, yes—just,” Armin says, each word a trial, “please.”  
  
Bertholdt is awfully slow, at first. His thumb runs over the slit, then under the ridge of the head of his cock, a steady rhythm which leaves Armin straining upwards for more. There’s something pleasant starting to come through the wall of pain, something more than just the ache, so close Armin could almost reach out and take it.   
  
“You two can,” he breaks off into a moan as Bertholdt gives his cock a particularly hard pull, wrist twisting just the way he likes, “ah, move again. I can—can take it, I think.”  
  
Reiner gives an odd little laugh at that. Armin can feel the pull of a grin where his mouth is pressed into the crook of Armin's neck. “If you’re sure,” he says, and he shifts, forcing Armin further up between the both of them. It sends a dizzying rush of pleasure and pain through him, the blunt pressure sudden and hard against his prostate. It must take Bertholdt by surprise, too, because his hand jumps from Armin’s cock to the jut of his hipbone, as if to steady him.  
  
“Reiner,” Bertholdt says, a strange tightness to his voice.  
  
Reiner just laughs again. His hands skims along Armin’s ribs, at the muscle corded there, and pins Armin tight against his chest with one arm, the other reaching around Bertholdt’s side to bring them closer together. Pressed between them, Armin can’t help but remember how strong they both are, but the rising panicky tide of helplessness fades as quickly as it comes. He’s not afraid of Reiner or Bertholdt. He has no reason to be.  
  
A moan escapes him when Reiner rolls his hips, slow and deliberate and deep, ducking his head to mouth at Armin’s collar. His teeth scrape along the prominent line of his clavicle, not enough to hurt but then it  _does_ , because Reiner bites down hard at his pulse point. It’s going to leave a bruise but Armin doesn't care, not when Bertholdt rocks forward at the same time and the pain flares back to pleasure. Reiner hums into the skin of his throat, a content little note, before pulling away with a pop. He must be saying something because his mouth is moving, but Armin can’t think beyond how lovely his lips look, all red and wet, and desperate, disconnected thoughts rush through his head—what Reiner’s mouth would feel like around his cock, or Bertholdt’s, or— _fuck_ , both of them, their clever tongues and teeth and hands. Armin moans at the thought of losing himself to this.  
  
Fingers reach up into his hair and pull, jarring him back into reality. It’s Bertholdt’s hand, he realises, and he tugs Armin’s head back far enough that he’s craned over Reiner’s shoulder, exposing the pale underside of his jaw. Bertholdt dips close, letting his teeth glance along the tender flesh there, at the red, sore spot where Reiner’s mouth was only moments before. His eyes are glassy, wide, almost glowing in the dark of the room. Armin can catch the change in them when Reiner begins to move again, canting his hips to fuck him with shallow thrusts.  
  
Reiner says Bertholdt’s name very softly, reaching for his hand and lacing their fingers together around Armin’s narrow waist. Reiner must be close: his breathing has changed, gone hard and short, the pace of his thrusts faster now. He tells Armin how good he feels, how good Bertholdt feels with him, against him, a familiar pitchy edge to his voice as he fucks into him, hard and deep. Armin’s exhale leaves him in a whimper, because as much as it hurts it feels good, too—and he  _likes_  the hurt, the way it keeps him lucid, keeps him close but not quite close enough.  
  
Reiner stiffens, and Armin knows from his shuddering gasp and the way his cock pulses that he’s coming, his body a taut line flush along his spine. Bertholdt gives a startled moan in response. Armin wonders whether he can feel it the way he can—every twitch of Reiner’s cock pressed tight against his, the heat of his release, the wonderful edge rolling through him.   
  
A beat passes, and Reiner groans shakily, slipping out of Armin as he settles back against the headboard. It leaves Armin feeling embarrassingly empty, even with Bertholdt still inside him. Reiner pulls at his hips, encouraging Armin into the cradle of his lap and grunting when he brushes against his soft cock, still sensitive from coming only moments ago. Bertholdt follows obligingly, grip sure on Armin’s waist as they readjust. The muscles of his jaw tense and relax, flitting, Armin notices, like he’s fighting back his own orgasm.   
  
Reiner is saying something, mumbling soft words of encouragement that Armin can't quite catch with the blood roaring in his ears, but he lets himself get swept up in it, each of Bertholdt's thrusts rocking him, up and back into Reiner’s chest. He can hear the headboard creaking in protest. Armin drops his head back to the junction of Reiner’s shoulder, a familiar heat pooling in the base of his stomach. He’s so caught up in Bertholdt's rhythm—slower than Reiner’s tends to be, sweeter, almost—that he doesn’t notice Reiner’s hand till it’s wrapped firm about his straining erection. He beats Armin off with smooth, easy strokes, each even pull of his fingers making his insides contract, the coil of arousal in his belly going tight when Reiner thumbs the head of his cock.

It doesn’t take long for Armin to come, not with Reiner’s sure grip and the way Bertholdt slides almost all the way out before driving back in. The force of it knocks the air out of him, a bright flare of  _too-much_  leaving Armin open-mouthed and wordless, arching up on his heels like someone’s reached inside of him and pulled. He’s barely aware of Bertholdt fucking him through it, panting hot and staccato into his ear as Armin contracts around his cock. It isn’t long before Bertholdt seizes up too, a hand clapped against his mouth to muffle his moan as he thrusts forward one final time.  
  
They stay like that for a while, Bertholdt growing soft inside him, Armin limp against Reiner’s chest as he gasps for air. He still feels a little—floaty, like he’s yet to come back to earth, never mind get up and go anywhere. It must be some minutes before Bertholdt eventually pulls out of him, trying to separate himself from their mess of limbs. The sensation makes Armin wince, over-sensitive, come trickling out from between his legs.   
  
“Oh no you don't,” Reiner says, sounding tired but amused. He grabs at Bertholdt’s forearm and, with perhaps more force than necessary, yanks him back into their pile of person. Armin watches as Reiner tucks his arms around the both of them, the satisfied way he closes his eyes. “We’re not needed anywhere, are we?”  
  
Bertholdt mumbles something, but there’s no challenge in it, and eventually he’s sinking back against the both of them. The sweat on his skin has cooled a little, but it’s not unpleasant.  
  
Armin closes his eyes. After all, Reiner’s right. They’re not needed anywhere, not right now. And, to be honest, Armin doesn't think there’s many places he’d rather be than here, with his legs entwined with Reiner’s and Bertholdt’s both, the afterglow leaving him warm, sore, happy. For now, at least, everything else can wait.


End file.
